Which messaging app are your using? If you are using Google Messages and have RCS activated, you can go into the group, tap the three dots on the top right, go to group details and tap on "leave group". I am unclear whether you can remove yourself from a group you started, as I have not started any groups of my own, but you likely can. If you are in a group chat with people who are known to you, the process is the same. If you got added to a random group chat from a stranger, that is a phishing exercise, and you can just mark that chat as spam and it will be sent to the spam folder in Google. Do not interact with it in any way, not even to remove yourself. If you are leaving a group, inform the group you are exiting and then do as above.
I don't believe there's a way to do it in Samsung messages, but I don't know for sure.
